In architecture you usually want an uneven number of openings in a repetitious facade as it allows the entrance to be placed in the center. The greek temples (with one or two execptions I think) had an even number of columns but uneven number of voids.
That tradition and the function of it is I think is one of the reasons five windows seem more natural. A funny quirk of language when you say five columns when in architecture speak it would be six columns. Because columns are the load bearing vertical element not the window.